1. Field of the Invention
In recently manufactured automotive vehicles, various safety measures have been taken in order to protect a driver of the vehicle during an accident. One known measure of this kind is to install a collapsible steering shaft, adapted and designed to axially collapse, so as to absorb or diminish an axial impact force applied to the driver's body from a steering wheel when the driver is thrown forwards from the driver's seat and collides with the steering wheel during a collision, in particular a front end, head-on collision.
Many vehicles have steering column covers attached to the top of the steering shaft so as to conceal the steering shaft between the steering wheel and an instrument panel or dashboard. Such a steering cover is usually located in front of the instrument panel and, therefore, overlaps with it. In an automotive vehicle, however, the collapsible steering shaft is not always effective to protect the driver against injury during a head-on collision. This is because although the steering shaft axially collapses and allows the steering shaft cover to displace when an axial force is applied to the steering wheel by the driver's body as it is thrown forwards from the driver's seat during the head-on collision, the steering shaft cover is obstructed by the instrument panel. Therefore, movement of the collapsible steering shaft is restricted, and an insufficient steering shaft collapse results.
2. Description of Related Art
To eliminate such a restriction of steering shaft collapse, it has been proposed to provide an instrument panel structured so as to be partly breakable by an impact applied by the column cover in order to allow the collapsible steering shaft to collapse sufficiently for driver protection. Such an instrument panel structure is known from Japanese Unexamined Patent Application No.55-101315, entitled "Concealing Panel Structure of Instrument Board," filed on July 25, 1980 and laid open as Japanese Unexamined Patent Publication No.57(1982)-26018 on Feb. 12, 1982.
The breakable part of the instrument panel has to be dimensioned so as to provide a sufficient area for the steering column cover to sink. This typically results in a jutted instrument panel configuration.